Fixed frequency difference stablilization system



Sept. 8, 1942. R. H. VARIAN ET AL FIXED FREQUENCY DIFFERENCESTABILIZATION SYSTEM Filed Nov. 20,

INVENTORS RUSSELL H. VARIAN WILLIAM W. HANSEN e TO VOLT. LIMITER 32Patented Sept. 8, 1942 FIXED FREQUENCY DIFFERENCE ICE STABILIZATIONSYSTEM Russell H. Varian, William W. Hansen, and Edward L. Ginzton,Stanford University, Calif.,

assignors to The Board of Trustees of The Leland Stanford JuniorUniversity, Stanford University, Calif.

Application November 20, 1940, Serial No. 366,358

6 Claims.

This invention relates, generally, to apparatus for maintaining ultrahigh frequency oscillators at a desired frequency difference, and theinvention has reference, more particularly to a novel fixed frequencydifference stabilization system for accomplishing this purpose.

It is often desirable in ultra high frequency work such as whenmeasuring distances to be able to maintain two ultra high frequencyoscillators at a fixed frequency difference without variation. Thus, itmay be desirable to maintain two oscillators operating at frequencies ofthe order of 3x10 cycles per second at a fixed frequency difference offrom 500 to 100,000 cycles per second. This type of apparatus is alsouseful for other purposes such as in medicine and wave guidecommunications.

The principal object of the present invention is to provide a novelfixed frequency difference stabilization system adapted to maintainultra high frequency oscillators at a fixed frequency difference andwithout variation of such difference.

Another object of the present invention is to provide, in connectionwith ultra high frequency oscillators, a low frequency master oscillatorto be used in determining and maintaining the desired fixed frequencydifierence between the ultra high frequency oscillators, the beatfrequency between the latter oscillators being combined with the outputof the master oscillator for purposes of control.

Other objects and advantages will become apparent from thespecification, taken in connection with the accompanying drawing whereinthe invention is embodied in concrete form.

In the drawing, Fig. 1 is a wiring diagram of i Referring now to Figs. 1and 2 of the drawing, the reference numeral I designates one ultra highfrequency oscillator of the order 3x10 cycles per second, whereas,reference numeral 2 designates another such oscillator which is to bemaintained at a fixed frequency difference with respect to oscillator I.

excited hollow resonator type as shown in Patent No. 2,242,275, issuedMay 20, 1941, in the name of Russell H. Varian. In oscillator I,electrons leaving the cathode 3 are accelerated by the acceleratingbattery 4 and pass through hollow resonators 5 and 6 successively whichare intercoupled by the concentric line 1 and the loops shown to. effectfeed-back coupling. Resonator I 5 serves to efiect' recurring changes invelocity of the electrons of the stream thereby effecting grouping ofthe electrons between the two resonators 5 and 6 so that the groupedstream on entering resonator 6 serves to set up strong oscillationstherein, i. e., interchanges energy with the field of 6.

A third resonator 8 is used in connection with the oscillator I throughwhich electrons pass after leaving resonator 6 to thereby set uposcillations in resonator 8 of the same frequency as obtained inresonators 5 and 6. There is no feed-back coupling between resonator 8and resonator B so that the former serves as a buffer resonator forpurposes which will appear later.

Oscillator 2 also comprises two resonators 5' and 6' which are excitedby an electron stream emitted from cathode 3' and caused to pass throughthe resonators by the accelerating battery 4'. A triode 9 is includedbetween'the positive side of the battery 4' andground to whichresonators 5 and 6' are connected.

A feed-back I is provided between resonators 5' and 6'. Metal inserts I0and II of the type shown in Patent No. 2,259,690, issued October 21, 1941, in the names of William W. Hansen, Russell H. Varian, and John R.Woodyard, are adjustably movable into the electromagnetic fields ofresonators 5 and 6' for the purpose of varying the frequency ofoscillator 2.- The inserts I0 and I I are shown connected to be operatedfrom a motor I2, the field windings of which are shown controlled froman amplifier I3.

The field within resonator 5' is shown cou-' pled through use of loopsand a concentric line It to the-buncher resonator I5 of a mixerdetectorI6 having a catcher resonator II. This mixer-detector has anaccelerating battery I8 for driving electrons through resonators I5 andI1. pling loops and concentric line I9 shown to the bufier resonator 8of oscillator I. Thus, since resonator I5 is excited at the frequency ofoscillator 2 and as resonator I1 is excited at the frequency ofresonator 8 due to the concentric line connections, the electron streamleaving reso- Oscillators I and 2 are of the electron beam 5 nator I!will have two component frequencies;

Resonator I1 is coupled with the cou:

that of oscillator I and that of oscillator 2, which are detected by thedetector grid 20 and cooperating plate 2|, as shown in the abovementioned Patent No. 2,259,690.

Actually the grid 20 segregates the electrons according to theirvelocities so that only a portion of the electrons are collected byplate '2I which is one way of effecting detection. If desired,concentric line I 9 could be connected from resonator 8 to resonator I5.Also, the concentric line I4 could connectelther resonator 5' or 6' toeither resonator I5 or II. However, the

. connections shown in the drawing are deemed best since they providecomplete isolation between osclllators I and 2 and prevent any tendencytoward synchronization, i. e., zero beat frequency between the two.Since there is no feedback coupling between resonator 8 and resonator 5of oscillator I, there is no tendency of the mixer-detector to alter thefrequency of the oscillator I, which would otherwise occur if thismixer-detector were coupled directly to the resonator 5. v

The A. C. component of the detector output appears across resistor 23and is passed through condenser 22 and, hence is applied to the input ofthe audio amplifier 24, the output of which is applied to a voltagelimiter 26, the output of which, in turn, is applied miseries to primarywinding 21 of a transformer 28 and to one primary winding 29 of a secondtransformer 30.

A master oscillator 3| of a frequency corresponding to the desiredfrequency difference between the controlled oscillators is shownconnected to voltage limiter 32. Preferably the master oscillator 3I isadjustable as to frequency as by knob 33 so that this oscillator may beoperated at any desired frequency of a suitable range of frequencies asfrom 500 to 100,000 cycles per second, although lower or higherfrequencies can be used.

Voltage limiter 26 is adjustable as is also voltage limiter 32 so thatthe magnitude of the voltage output of limiter 32 can be madesubstantially the same as that of limiter 26. The system is so designedthat as long as oscillators I and 2 maintain the desired frequencydifference as determined by oscillator 3| and the outputs of the twovoltage limiters are exactly 90 out of phase, then no correction as tofrequency takes place. The output of voltage limiter 32 is suppliedthrough a primary winding 34 of transformer 28 and reversely throughprimary winding 35 of transformer 30. Thus, as shown by arrows of Fig.1, the voltage output of limiter 26 and that of limiter 32 are additivein trans former 28 and are subtractive in transformer 30.

Thus, referring now to Fig. 2, if the voltage output of limiter 26 isdesignated in and that of limiter 32 is designated as 02, then if thesevoltages are at right angles as shown in solid lines in the left handportion of Fig. 2, the solid line resultant n will be applied to thetransformer 28, while the differences of these voltages, i. e., 112-211shown in solid lines in the right hand portion of Fig. 2 will have asolid line resultant T2 which will be applied to the transformer 39.Transformer 28 is shown provided with a divided secondary winding 36having its outer ends connected to the plates of diodes 3'! and 38 andhaving its center connected through a resistance 39 and a by-passcondenser 65 to the cathodes of these diodes. Similarly, the transformer30 has a divided secondarywinding 49 having its outer ends: connected tothe 'plates ofdiodes 4| and 42, whereas its center tap is connectedthrough a resistance 43 and by-pass condenser 6| to the cathodes ofrectifiers and 42. Lead 44 connects the two resistances 39 and 43 inseries.

Thus, with the voltages supplied from the voltage limiters of the valuesshown in solid lines in Fig. 2, there will appear across resistor 39 aD. C. voltage proportional to vector 11, whereas there will appearacross resistor 43 a voltage proportional to vector 12. Since vectors )1and r: are equal in magnitude, these voltages across resistors ,39 and43 being connected in opposition will cancel so that lead 45 connectedto the center tap winding 36 will have no volta e but will be at groundpotential since a lead 46 connects the corresponding center tap ofwinding 40' of the ground. However, should the frequency differencebetween oscillators LI and 2 shift slightly by a small portion of acycle, then the output of voltage limiter 26, i. e., 7.71 will shift inphase as shown in Fig. 2 so that the sum of this shifted phase voltagetogether with voltage 02 will produce the dotted line resultants n andr2 shown in Fig. 2, which resultants are of different magnituderesulting in different voltages appearing across resistances 39 and 43so that a voltage app ars upon lead 45 and is supplied to the grid oftriode 9 and to the D. C. amplifier I3. This voltage appearing on lead45 serves to increase or decrease the resistance of. tube 9 dependingupon the direction of the phase shift of vector 01, which, in turn,depends upon whether the difference in the frequency between oscillatorsI or 2 is increasing or decreasing. Thus, the effective acceleratingvoltage of oscillator 2 is varied by tube 9 to alter the frequency ofoscillator 2 to correct for the change in frequency differences. Thiscorrection in frequency is aided by the action of amplifier I3 operatingthrough motor I2 to move the plungers I8 and II. If desired, either thetube 9 or the plungers I0 and II could be used alone in correcting thefrequency changes. Thus, it will be seen that any shift from thepredetermined frequency difference between oscillators I and 2 willeffect a corresponding phase shift in the output of mixer-detector I6and in the output of voltage limiter 26, thereby causing the desiredcorrection to take place to maintain the frequency difference fixed asdetermined by the frequency of master oscillator 3'I.

In the modification shown in Fig. 3, the t: ansformers 28 and 39 areeliminated. This may be desirable since these transformers may produce aslight phase shift. In Fig. 3', the output of voltage limiter 26 isconnected to phase inverter 48 so that the voltage appearing acrossresistor 49 of this phase inverter will be in inverted phase and havethe same value as the output of voltage limiter 2B. This voltage isapplied to one grid of a double-grid difference voltage amplifier tube5| having its other grid connected to voltage limiter 32. A double-gridsum amplifier H has one grid thereof connected across resistor 52 of thephase inverter having the same A. C. voltage as that across resistor 53of this inverter so that the voltage applied to tube 5I from resistor 52will be equal to and in phase with the voltage output of limiter 26. Theother grid of tube 5I is connected to voltage limiter 32. The A. C.output of tube 50 is connected through condenser 54 and appears acrossresistor 55 for application to diode 56 so that a rectified D. C.voltage appears across a resistance 51 in the circuit of tube 56 whichis proportional to the difi'erence resultant T2 of Fig. 2.

Likewise, a D. C. voltage appears across a resistance 58 of rectifier 59in the output of tube 5| which voltage is proportional in magnitude tothe resultant n, which is the sum of vectors in and v2. Resistors 51 and58 are connected in series opposition and through lead 45 as describedin connection with Fig. 1, to the grid of tube 9 (see Fig. l) and to theD. C amplifier I3, as previously explained. The operation of thestructure of Fig. 3 is otherwise similar to that of Fig. l and wouldappear to require no further description. v

As many changes could be made in the above construction and manyapparently widely different embodiments of this invention could be madewithout departing from the scope thereof, it is intended that all mattercontained in the above description or shown in the accompanying drawingshall be interpreted as illustrative and not in a limiting sense.

The fixed frequency difference stabilization system of this invention isparticularly valuable in wave guide communication for maintainingseparate frequency channels at the desired fixed frequency differences.

What is claimed is:

1. A fixed frequency difference stabilization system comprising aplurality of ultra high frequency oscillators having electron beamexcited electron grouping and energy interchanging resonators, means forvarying the frequency of at least one of said oscillators by varying anoperating characteristic thereof, mixer-detector means having resonatorsrespectively connected to said oscillators, a master frequencyoscillator, means connected for producing a voltage comprising the sumand difference of a version of the output voltages of saidmixer-detector means and said master oscillator, and means connectingsaid produced voltage to said frequency varying means for controllingthe latter to maintain said ultra high frequency oscillators at a fixedfrequency difference.

2. A fixed frequency difference stabilization system comprising ultrahigh frequency oscillators, a mixer-detector connected to saidoscillators for producing a heat frequency, means for amplifying theoutput of said mixer detector, a master oscillator, voltage limitermeans for limiting the voltage outputs of said amplifying means and saidmaster oscillator, means for adding and subtracting said limited voltageoutputs, and means utilizing the resultants of said voltage addition andsubtraction to control the relative frequency of said ultra highfrequency oscillators.

3. A fixed frequency difference stabilization I system comprising ultrahigh frequency oscillators, a mixer-detector connected to saidoscillators for producing a beat frequency, means foramplifying thealternating current output of said mixer-detector, a master oscillator,voltage limiter means for limiting the alternating current voltageoutput of said amplifying means and said master oscillator, means foradding and subtracting said limited voltage outputs, means forrectifying the resultant sum and difference voltages, frequency varyingmeans, and means connecting the rectified voltages in opposition andconnected to said frequency varying means for controlling the relativefrequency of said ultra high frequency oscillators.

4. In a fixed frequency difference stabilization system, electron streamexcited oscillators comprising spaced electron stream velocity changingand energy interchanging hollow resonators, a mixer-detector, one ofsaid oscillators having an additional buffer resonator unilaterallycoupled by the electron stream to the velocity changing and energyinterchanging resonators of such oscillator, and means coupling saidbufier resonator and one of the resonators of said other oscillator tosaid mixer-detector.

5. In a fixed frequency diiference stabilization system, electron streamexcited oscillators comprising spaced electron stream velocity changingand energy interchanging hollow resonators, a mixer-detector also havingspaced electron stream velocity changing and energy interchanging hollowresonators, one of said oscillators having an additional bufferresonator unilaterally coupled by the electron stream to the velocitychanging and energy interchanging resonators of such oscillator, andmeans coupling said buffer resonator and one of the resonators of saidother oscillator to said mixer-detector, said buffer resonator servingto prevent one of said oscillators from directly influencing thefrequency of the other, said mixer-detector having detector means for.segregating electrons according to their velocities.

6. In ultra-high frequency oscillator apparatus, an electron streamexcited oscillator comprising means producing an electron stream,velocity changing, energy interchanging and buffer hollow resonatorsmutually spaced apart in succession along the stream, mechanical meanscoupling said velocity changing and energy interchanging resonatorstogether, said buifer reso-.- nator being but unilaterally coupled tosaid other resonators by the electron stream, and means for extractingoscillator output energy from said bufier resonator, said bufferresonator servingto prevent said energy extracting means from vary ingthe frequency of said oscillator.

RUSSELL H. VARIAN.

WILLIAM W. HANSEN. EDWARD L. GINZTON.

